This invention relates to automation for placing covers on shipping cassettes and taking covers off shipping cassettes.
Magnetic disks are typically shipped in plastic cassettes, such as the cassettes described in U.S. Pat. No. 4,557,382, issued to Douglas M. Johnson on Dec. 10, 1985, and incorporated herein by reference. FIGS. 1A to 1D show a cassette 1 which includes slots 2 for receiving magnetic disks 3 (shown in FIG. 2).
Cassette 1 includes a top opening 4 for receiving a top cover 5 and a bottom opening 6 for receiving a bottom cover 8.
Bottom cover 8 includes a rim 10 which surrounds and mates with walls 12 at the bottom of cassette 1. Bottom cover 8 is held on cassette 1 by a friction fit. The top of cassette 1 includes a rim 27, which is received by a slot 28 in top cover 5.
As can be seen in FIG. 1B, the sides of cassette 1 include slots 16 surrounded by slot rims 18. The sides of top cover 5 include tongues 20 which cover slots 16 when top cover 5 is placed on cassette 1. A catch 23 (on each of the tongues 20) engages with one of rims 18 to hold top cover 5 in place. Each catch 23 includes a slanted bottom surface 24 (FIGS. 1C and 1D) such that if one pushes top cover 5 downward over rims 18, tongues 20 are pushed outwardly in the direction of arrows A until catches 23 pass rims 18. When catches 23 pass rims 18, tongues 20 snap back and catches 23 engage with rims 18. To remove top cover 5 from cassette 1, one must pull tongues 20 outwardly (again, in the direction of arrow A) prior to lifting top cover 5 from cassette 1.
Of importance, when top cover 5 and bottom cover 8 are placed on cassette 1, magnetic disks within the cassette are completely enclosed and protected from dust and other contaminants. Cassette 1 is typically used to transport the disks to different manufacturing stations during the disk manufacturing process (e.g. to stations where the disks are plated, textured, cleaned, sputtered or lubricated) and to ship disks to customers. It is desirable to automate as much of the manufacturing process as possible, and it is known in the art to provide automation which removes top cover 5 and bottom cover 8 from cassette 1 during various manufacturing steps, and then places the top and bottom covers back on the cassette.
Many of the manufacturing steps during magnetic disk manufacturing require extremely clean environments, e.g. a "class 10" manufacturing environment. (Class 10 is a manufacturing standard established by the International Standards Organization, or ISO.) We have discovered that if the machinery used to place top cover 5 onto cassette 1 simply pushes top cover 5 downward so that catches 23 are pushed outward and then snap back over rims 18, contamination particles can be generated when catches 23 snap back over rims 18. These contamination particles can cause problems during disk manufacturing and use, and negatively impact yields.